Electronic ignition system for an internal combustion engine

ABSTRACT

A plurality of magnets rotated by the engine induces an alternating current voltage in a winding for charging the ignition capacitor, the discharge of the capacitor being controlled by a thyristor of which the control electrode is connected to a winding in which is induced, one each complete rotation of the magnets, a control voltage. Two neighboring magnets have extension pieces that cooperate with the core of the control winding to induce therein the control voltage, the remaining magnets being so positioned with respect to the core that during rotation these magnets induce no control voltage.

Unite States atent [191 Schmaldienst et a1.

[ 1 June 5,1973

[75] Inventors: Peter Schmaldienst, Nurnberg; Giinter Brand, Stuttgart,both of Germany [73] Assignee: Robert Bosch Gmbl-l, Stuttgart, Germany22 Filed: July 7, 1971 [2]] Appl. No.: 160,413

[30] Foreign Application Priority Data July 7, 1970 Germany ..P 20 33484.3

[52] US. Cl ..123/l48 E, 123/149 D, 123/148 R, 123/148 S [51] Int. Cl..F02d 1/00 [58] Field of Search ..123/148 E [56} References CitedUNITED STATES PATENTS 3,623,467 11/1971 Piteo ..l23/l48 E 3,630,18512/1971 Struber ..123/l48 E 3,599,615 8/1971 Foreman... ..123/148 E3,598,098 8/1971 Sohner ..l23/148 E 3,554,179 1/1971 Burson........123/148 E 3,500,809 3/1970 Hohne ..123/148 E Primary ExaminerLaurenceM. Goodridge Assistant Examiner-Ronald B. Cox Attorney-Michael S.Striker [57] ABSTRACT A plurality of magnets rotated by the engineinduces an alternating current voltage in a winding for charging theignition capacitor, the discharge of the capacitor being controlled by athyristor of which the control electrode is connected to a winding inwhich is induced, one each complete rotation of the magnets, a controlvoltage. Two neighboring magnets have extension pieces that cooperatewith the core of the control winding to induce therein the controlvoltage, the remaining magnets being so positioned with respect to thecore that during rotation these magnets induce no control voltage.

7 Claims, 3 Drawing Figures ELECTRONIC IGNITION SYSTEM FOR AN INTERNALCOMBUSTION ENGINE BACKGROUND OF THE INVENTION The invention relates toan electronic ignition system for an internal combustion engine, thesparking of the one or more spark plugs being controlled by a controlvoltage that is induced in a control winding carried by a magnetic coreand conducted to the control electrode of an electronic switch, such asa thyristor.

Among these electronic ignition systems of the prior art, it is known toprovide a rotatable magnetic system, which comprises a plurality ofmagnets that, with respect to the axis of rotation, are radiallypolarized and are mounted on a hollow, cylindrical, short circuitingpart. These magnets are spaced apart in the direction of thecircumference of the cylindrical short circuiting part. The polarity ofthese magnets alternates, there being an alternating current windingcarried by an iron core, in which winding an alternating current isinduced when the magnets rotate. Two lines, each drawn from the axis ofrotation through the center of a respective end face of the core, liealong different radii of the cylindrical short circuiting part, whichlatter is part of a cup-shaped body of rotation, which has an inwardlyextending connecting hub.

Internal combustion engines that are provided with an ignition system ofthis kind are usually intended for modern light motorcycles, the currentbeing provided by a flywheel magneto or by a flywheel generator magnetoso as to avoid the necessity of having a battery. The aforesaidalternating current winding can be used, for example, to charge theignition capacitor, which, by triggering the aforesaid electronicswitch, can be discharged through the primary winding of a spark coil,the sparkplug being connected across the secondary winding of this coil.To power the lamps and the horn there is usually provided a secondalternating current winding carried by another iron core. The samemagnetic system induces an alternating current in the secnd winding. Inorder to obtain an alternating current voltage of sufficiently highfrequency, the magnetic system must have as many magnets as possible. Ifthese same magnets would be used to induce the control voltage in theaforesaid control winding, the control voltage would cause too manyignitions and at times that would damage the engine, since in most casesonly a single ignition is required for each complete rotation of themagnetic system.

With these electronic ignition systems of the prior art, there isprovided a further rotatable magnet that is moved past the magnet yokecarrying the control winding at the ignition point. This ensures thatthe spark plug is sparked only when the piston in the cylinder issufficiently near to top dead center. To avoid troublesome leakage flux,this further magnet is enclosed by a magnetic shield, a fact that addsto the cost and complexity of the ignition system.

SUMMARY OF THE INVENTION An object of the invention is an electronicignition system for an internal combustion engine that avoids a specialmagnet for obtaining the ignition control voltage. 1

Briefly, the invention consists of a magnetic system, the magneticsystem including a plurality of permanent magnets spaced about a commonaxis and defining a cylinder, means for mounting the plurality ofmagnets free to be driven in rotation by the engine about this commonaxis, an electronic switch for permitting when conductive the productionof an ignition causing spark, a stationary magnetic core located withinthe cylinder and having two spaced end faces located opposite saidplurality of permanent magnets, the respective centers of said end faceslying in a common radial plane of the cylinder, a control windingcarried by the magnetic core and connected to the switch for generatinga control voltage to control the conductivity of the switch when theplurality of permanent magnets rotates, and wherein each magnet of thisplurality of permanent magnets is polarized along a radius of thecylinder, successive magnets of the plurality of permanent magnetshaving alternating polarity, this plurality of permanent magnetsincluding first and second neighboring magnets, the plurality of magnetsexcepting these first and second magnets being so positioned withrespect to the magnetic core that no voltage is induced in the controlwinding when the plurality of magnets rotates, the first magnetincluding an extension of one pole, this one pole being positionednearer to the two end faces when the first magnet is moved past themagnetic core than the other pole of the first magnet, the second magnetincluding an extension of the other pole, this other pole being theopposite of the one pole and being positioned nearer to the two endfaces when this second magnet is moved past the magnetic core than theopposite pole of the second magnet, the two extensions projecting inopposed directions part way into the common space between the first andsecond magnets, the two extensions being spaced apart in a directionparallel to the common axis and in a predetermined rotational positionof the plurality of permanent magnets being aligned with respective onesof the end faces of the magnetic core so as to induce in the controlwinding a full wave alternating current voltage when the plurality ofmagnets rotates, of which full wave one half wave is used as the controlvoltage, and a charging winding located within the cylinder for havinginduced therein, when the plurality of permanent magnets rotates, analternating current voltage for charging the ignition capacitor.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric view, partlycutaway, of the ignition system incorporating the improvement of theinvention, the isometric view including a wiring diagram of the electriccircuit;

FIG. 2 is an isometric view of one embodiment of the core for thecontrol winding; and

FIG. 3 is an isometric view of a second embodiment of the core for thecontrol winding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, theignition system illustrated, which is intended for an internalcombustion engine, now shown, comprises an ignition capacitor 11 ofwhich one plate is connected to the ground rail 12 and the other plateis connected to the cathode of a rectifier 13. The anode of therectifier 13 is connected to the terminal 14 of an alternating currentwinding 15, which serves as the charging winding, the other terminal 16of this winding being connected to the ground rail 12. The ungroundedplate of the ignition capacitor 11 is also connected by the primarywinding 17 of a spark coil 18 to the output electrode 19 of a thyristorthat operates as an electronic switch 20, the reference electrode 21 andthe control electrode 22 of the thyristor respectively being connectedto the ground rail 12 and to to the cathode of a control diode 23. Theanode of the control diode 23 is connected to the control terminal 24 ofa control winding 25, the reference terminal 26 of which is connected tothe grounded rail 12. The spark coil 18 also includes a secondarywinding 27 across which is connected the spark plug 28, one end of thesecondary being connected to the grounded rail 12.

The alternating current winding is mounted on an iron core 29, and islocated along a chord of a circular path along which move the magnets Mof a magnetic system M, the magnets being moved in the direction of thearrow P by the internal combustion engine. Each of the magnets M (threebeing shown, although there are four in this particular embodiment) isin the form of a shell, the outer faces of which are fixed to the innerwall 30 of a hollow, cylindrical, magnetic short circuiting part 32.This part is a component of a cup-shaped body of revolution 31, which ismade of a magnetiferous material and incorporates a central, downwardlyprojecting, hub 34. The hub 34 incorporates a central bore 33, whichaccepts a shaft W that is rotated by the internal combustion engine.

The magnet M are radially polarized, as shown in FIG. 1, the north andsourth poles being designated by the respective reference letters N andS. The magnets M are spaced from one another a distance Z in thedirection of rotation, the active poles (those poles nearest to the ends35 and 36 of the core 29) of successive magnets being of alternatingpolarity as they are moved by the end faces 35 and 36. The angle ordefined between the radii r1 and r2, which begin at the axis of rotationO and pass through the centers a1 and a2 of these end faces, is sochosen that when a N pole passes by the end face 35 an S pole passes bythe end face 36, or the reverse is true, or else when a spacing Z passesby the face 35 another spacing Z passes by the face 36. The alternatingcurrent winding 15 and the iron core 29 therefor are mounted on acircular plate 37, which is rigidly fixed to the internal combustionengine, and which incorporates a central opening 38 for the hub 34 andthe shaft W.

Also fixed to the plate 37 is an iron core 39, which carries the controlwinding 25. The iron core 39 is so positioned with respect to themagnets M that the centers of the two end faces 40 and 41 of the core 39lie in the same radial plane with respect to the axis 0.

The control voltage for the switch 20 is induced in the winding 25 bytwo neighboring magnets M1 and M2 of the magnets M. The magnets M1 andM2 have each a respective tongue-like extension 42 and 43 of arespective active N and S pole, these extensions projecting into thecommon space Z between these two magnets. The extensions 42 and 43 arespaced apart a distance b in the axial direction, just as are the faces40 and 41; and in a predetermined rotational position (shown in FIG. 1)of the magnetic system M they are aligned with, or cover, respectiveones of the end faces 40 and 41, so that three edges of a face 40 or 41are aligned with three edges of a respective extension 43 or 42.

In the preferred embodiment each of the active poles of the magnets M iscovered with a magnetiferous plate L, the respective plates L1 and L2for the magnets M1 and M2" having each a respective tongue F1 and F2,which extends at least approximately concentrically with the part 32.These tongues constitute, in a very simple manner, the extensions 42 and43.

In order to ensure that the ignition is suitably dependent on theinstantaneous speed of the engine, it is desirable that at least one ofthe end faces 40 and 41 has an extension surface 44 (see FIGS. 2 and 3),which, in respect of the direction of rotation P of the magnetic systemM, precedes the end face 40 or 41. The extension surface 44 isincorporated by a magnetiferous extension piece 45, which is connectedto the iron core 39, the cross section through which the magnetic fluxis conducted being smaller than the cross section of the iron core 39.

A sufficiently large range of adjustment of the ignition timing isobtained by making the extension surface 44 contiguous with the endface, as shown in FIG. 2. The extension surface 44 is incorporated onthat part of the extension piece 45 that tapers, in the manner of acrescent, in the direction opposite to that in which the magnetic systemM rotates. In this case it is sufficient when the end face provided withthe extension surface 44 is that end face (here 41) that is aligned withthe extension 42.

If a sudden, stepped, ignition advance is desired when the engine speedexceeds a predetermined rpm, there can be provided a recess 47 betweenthe end face 40 or 41 and the extension surface 44, as shown in FIG. 3.In this embodiment it is advantageous if each of the end faces 40 and 41is provided with an extension surface 44.

When the magnetic system M rotates, the following occurs. As thespacings Z are rotated past the end faces 35 and 36 of the iron core 29that carries the altemating current winding 15, the changing flux in thecore 29 induces an alternating current voltage in the winding 15. Thosehalf waves of the alternating current voltage for which the diode 13 isconductive charge the ignition capacitor 11. Since the magnetic flux inthe core 29 changes several times for each complete rotation of themagnetic system M, the ignition capacitor 11 is sufficiently charged toensure a hot spark. If necessary, the

ignition capacitor 11 can be charged through a full wave bridgerectifier, so that each half wave of the voltage induced in thealternating current winding 15 is used to charge the ignition capacitor11.

In the present case, the ignition system is intended for a singlecylinder internal combustion engine, so that, if the magnetic systemrotates at the same speed as does the engine, there will be one ignitionfor each complete rotation of the magnetic system. This is ensured,because during one complete rotation of the magnetic system theextensions 42 and 43 are rotated past the end faces 40 and 41 only once,so that there is obtained only one complete cycle of alternating currentvoltage, that half wave thereof that is conducted by the diode 23 to thecontrol electrode 22 of the switch 20 triggering the latter. Theignition capacitor 11 can now discharge through the primary winding 17of the spark coil 18, so as to induce in the secondary winding 27 a highvoltage spike that produces a spark in the gap of the spark plug 28,which spark ignites the compressed fuel-air mixture in the cylinder ofthe engine.

The extension piece 45 shown in FIG. 2 by reducing the steepness of theleading edge of the control voltage pulse broadens the range throughwhich the ignition timing can be varied.

With reference to FIG. 3, the extension piece 45 causes a controlvoltage in the form of a full wave alternating current voltage when theextensions 42 and 43 pass by the extension surfaces 44. At a low enginespeed, the peak amplitude of this full wave is too small to reach thethreshold voltage of the thyristor 20, so that there is ignition onlywhen the extensions 42 and 43 pass by the end faces 40 and 41. When theengine speed exceeds a predetermined rpm, there is a sudden, stepped,advance of the ignition, because the control voltage caused by theextension surfaces 44 now has a sufficient amplitude to trigger theswitch 20.

If the internal combustion engine is intended, for example, for amotorcycle, the electric power for the lights and the horn can beobtained from the alternating current winding or from an additionalalternating current winding carried by a separate core, in which themagnetic system induces, as it does in the winding 15, an alternatingcurrent.

In accordance with the invention, the number of magnets M can be morethan four and/or more than one space Z can be provided with the poleextensions 42 and 43.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcircuits differing from the types described above.

While the invention has been illustrated and described as embodied inimprovements in an electronic ignition system for an internal combustionengine, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptions should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended:

1. An arrangement in an electronic ignition system, having an ignitioncapacitor, for an internal combustion engine having at least one sparkplug, comprising, in combination, a magnet system, said magnetic systemincluding a plurality of permanent magnets spaced about a common axisand defining a cylinder; means for mounting said plurality of magnetsfree to be driven in rotation by the engine about said common axis; anelectronic switch for permitting when conductive the production of anignition causing spark; a stationary magnetic core located within saidcylinder and having two spaced end faces located opposite the innerperiphcry of said cylinder, the respective centers of said end faceslying in a common radial plane of said cylinder; a control windingcarried by said magnetic core and connected to said switch forgenerating a control voltage to control the conductivity of said switchwhen said plurality of permanent magnets rotates, and wherein eachmagnet of said plurality of permanent magnets is polarized along aradius of said cylinder, successive magnets of said plurality ofpermanent magnets having alternating polarity, said plurality ofpermanent magnets including first and second neighboring magnets, saidplurality of magnets excepting said first and second magnets being sopositioned with respect to said magnetic core that no voltage is inducedin said control winding when said plurality of permanent magnetsrotates, the first magnet including an extension of one pole, said onepole being positioned nearer to said two end faces when said firstmagnet is moved past said magnetic core than the other pole of saidfirst magnet, the second magnet including an extension of the otherpole, said other pole being the opposite of said one pole and beingpositioned nearer to said two end faces when said second magnet is movedpast said magnetic core than the opposite pole of said second magnet,the two extensions projecting in opposed direction part way into thecommon space between said first and second magnets, said two extensionsbeing spaced apart in a direction parallel to said common axis and in apredetermined rotational position of said plurality of permanent magnetsbeing aligned with respective ones of said end faces of said magnet coreso as to induce in said control winding a full wave alternating currentvoltage when said plurality of permanent magnets rotates, of which fullwave one half wave is used as the control voltage; and furthercomprising a charging winding located within said cylinder for havinginduced therein, when said plurality of permanent magnets rotates, analternating current voltage for charging the ignition capacitor.

2. The arrangement as defined in claim 1 further including a respectivemagnetiferous plate covering that pole of each magnet of said pluralityof permanent magnets that is positioned nearer to said end faces of saidmagnetic core when the respective said magnet passes by the latterduring rotation of said plurality of permanent magnets, the respectiveplate of said first and second magnets having a tongue that comprisessaid extension, the surfaces of the two tongues at least approximatelydefining part of a common cylindrical surface that is located withinsaid cylinder and having as its axis said common axis.

3. The arrangement as defined in claim 1, further including amagnetiferous extension piece means incorporating a face that ispositioned opposite said plurality of magnets for extending the surfacearea of at least one of said end faces of said magnetic core in thedirection opposite to the direction of rotation of said plurality ofpermanent magnets, said extension piece being physically connected withsaid magnetic core and having a cross section smaller than that of thelatter.

4. The arrangement as defined in claim 3, wherein said face of saidextension piece means is contiguous with said one end face, said face ofsaid extension piece means tapering in the direction opposite to that ofthe rotation of said plurality of permanent magnets.

6. The arrangement as defined in claim 4, wherein said one end face isthat face which is aligned with that said extension of a pole thatcauses the control voltage.

7. The arrangement as defined in claim 5, wherein said extension piecemeans includes a respective extension for each of said two end faces ofsaid magnetic COI'C.

1. An arrangement in an electronic ignition system, having an ignitioncapacitor, for an internal combustion engine having at least one sparkplug, comprising, in combination, a magnet system, said magnetic systemincluding a plurality of permanent magnets spaced about a common axisand defining a cylinder; means for mounting said plurality of magnetsfree to be driven in rotation by the engine about said common axis; anelectronic switch for permitting when conductive the production of anignition causing spark; a stationary magnetic core located within saidcylinder and having two spaced end faces located opposite the innerperiphery of said cylinder, the respective centers of said end faceslying in a common radial plane of said cylinder; a control windingcarried by said magnetic core and connected to said switch forgenerating a control voltage to control the conductivity of said switchwhen said plurality of permanent magnets rotates, and wherein eachmagnet of said plurality of permanent magnets is polarized along aradius of said cylinder, successive magnets of said plurality ofpermanent magnets having alternating polarity, said plurality ofpermanent magnets including first and second neighboring magnets, saidplurality of magnets excepting said first and second magnets being sopositioned with respect to said magnetic core that no voltage is inducedin said control winding when said plurality of permanent magnetsrotates, the first magnet including an extension of one pole, said onepole being positioned nearer to said two end faces when said firstmagnet is moved past said magnetic core than the other pole of saidfirst magnet, the second magnet including an extension of the otherpole, said other pole being the opposite of said one pole and beingpositioned nearer to said two end faces when said second magnet is movedpast said magnetic core than the opposite pole of said second magnet,the two extensions projecting in opposed direction part way into thecommon space between said first and second magnets, said two extensionsbeing spaced apart in a direction parallel to said common axis and in apredetermined rotational position of said plurality of permanent magnetsbeing aligned with respective ones of said end faces of said magnet coreso as to induce in said control winding a full wave alternating currentvoltage when said plurality of permanent magnets rotates, of which fullwave one half wave is used as the control voltage; and furthercomprising a charging winding located within said cylinder for havinginduced therein, when said plurality of permanent magnets rotates, analternating current voltage for charging the ignition capacitor.
 2. Thearrangement as defined in claim 1 further including a respectivemagnetiferous plate covering that pole of each magnet of said pluralityof permanent magnets that is positioned nearer to said end faces of saidmagnetic core when the respective said magnet passes by the latterduring rotation of said plurality of permanent magnets, the respectiveplate of said first and second magnets having a tongue that comprisessaid extension, the surfaces of the two tongues at least approximatelydefining part of a common cylindrical surface that is located withinsaid cylinder and having as its axis said common axis.
 3. Thearrangement as defined in claim 1, further including a magnetiferousextension piece means incorporating a face that is positioned oppositesaid plurality of magnets for extending the surface area of at least oneof said end faces of said magnetic core in the direction opposite to thedirection of rotation of said plurality of permanent magnets, saidextension piece being physically connected with said magnetic core andhaving a cross section smaller than that of the latter.
 4. Thearrangement as defined in claim 3, wherein said face of said extensionpiece means is contiguous with said one end face, said face of saidextension piece means tapering in the direction opposite to that of therotation of said plurality of permanent magnets.
 5. The arrangement asdefined in claim 3, wherein said extension piece means incorporates arecess that extends in the direction away from said plurality ofmagnets, said recess being positioned between said face of saidextension piece means and said one end face.
 6. The arrangement asdefined in claim 4, wherein said one end face is that face which isaligned with that said extension of a pole that causes the controlvoltage.
 7. The arrangement as defined in claim 5, wherein saidextension piece means includes a respective extension for each of saidtwo end faces of said magnetic core.